Process for chemically modifying nylon with montmorillonite



Unite States This invention relates to improved nylon and to methods of making the same. Common synthetic linear polyamide compositions exhibit a tendency to accumulate static electric charges, usually of positive character, in use. This tendency, in the case of fibers and filaments, frequently complicates textile processing operations, such as picking, carding, drafting, spinning and weaving, as the fibers when frictioned build up high static charges which cause them to repel each other and balloon out, whereby control and further processing of the fibers becomes difiicult or impossible. Garment fabrics made of nylon exhibit an undesirable tendency to cling to the person, and nylon seat covers and carpets are prone to charge persons using them to the point of annoyance and discomfort, for example at the common experience of sparking when touching metal objects. Nylon also tends to soil easily, when both wet and dry, and the soil is tenacious and resists removal, suggesting an electrical bond.

It has been discovered that montmorillonite particles on the surface of nylon have the property of preventing static charge build-up and dry soiling. A principal object of the present invention is to provide novel methods for applying montmorillonite particles to nylon in a substantive manner, whereby the particles are fixed to the nylon. A related object is to provide nylon of permanently and positively controlled static properties, resistant to soiling when either Wet or dry, and readily cleaned. The treatment is simple and inexpensive, and may be readily combined with conventional dyeing procedures. Further objects will be in part evident and in part pointed out hereinafter.

Montmorillonite is a hydrous substituted aluminum silicate, with a micaceous structure and an exceptionally small ultimate particle size, less than 0.5 micron in maximum dimension. Montmorillonite is noted for its ability to swell in water, and disperses readily in cold water into particles of colloidal size. Varying proportions of calcium, magnesium and sodium ions are found in the cation exchange positions, depending on the source of the ma terial. Sodium montmorillonite is preferred in the present invention.

In accordance with the present invention, nylon is contacted with a dilute sol of montmorillonite in acid medium at elevated temperature for a period of time, usually from about minutes to about two hours, sufiicient to fix the montmorillonite particles to the nylon. The adhesion of the montmorillonite particles is substantive in character, to a degree apparently far exceeding the amount that would be held by mechanical entrainment. The invention is useful with all conventional synthetic linear po-lyamides, and while I do not desire to be bound thereby, a probable theory is that the nylon, when in acidic medium, adsorbs hydrogen ions onto the carboxyl oxygen of the peptide linkage. This apparently activates the terminal amino groups, causing them to assume a positive charge, which terminal amino groups then react with montmorillonite particles.

Example 1 Fifty pounds of raw stock, Du Pont Type 200, 3-denier, 1%" staple fiber, was placed in a standard dye machine of the Morton type, and water at 180 F. circulated through the stock for 20 minutes, to remove the finish.

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At the end of 20 minutes the hot water was drained, and the fibers rinsed with cold water until there was no more suds or foaming. As will be evident, in treating unfinished stock this preliminary wash may be omitted.

After draining the wash water, the machine was refilled with 600 pounds of a 0.5% sol of montmorillonite in water (600 pounds water and 3 pounds Volclay 200), and the pH of the sol then adjusted to 3.6 by adding 500 mls. glacial acetic acid. The pH of the sol in contact with the nylon rises gradually, to above 4, an initial pH of 3.6 efiecting an average pH of about 4 during the treatment.

The temperature of the treating medium was then raised to and maintained at 180 F., and the dye machin v operated to circulate the medium through the stock for one hour. The medium was then drained and the stock cooled by running cold water over the outside of the kier. The treated stock was then centrifuged to remove remaining sol and dried in an oven at F.

The treated nylon stable fiber can be carded, drafted and spun into yarn without accumulation of appreciable static charge, whereby these textile processes may be carried out efficiently and without difiiculty. The yarn may be made into carpet which not only exhibits controlled static properties, but resists both wet and dry soiling. The effect, moreover, is substantially permanent, since the fiber may be washed repeatedly without loss of its antistatic and anti-soiling properties. For example, a scouring bath may be made up of a gallon of water containing 0.2% soda ashand 1% detergent, such as Triton X-lUO, and 100 grams of fiber scoured therein at F. for 20 minutes, with occasional stirring. This severe scour may be repeated five times, and the fiber still exhibits the improved anti-static and anti-soiling properties. Presence of montmorillonite on the fiber may be demonstrated most simply by carding. Untreated stock builds up positive static charge and cards poorly, whereas treated stock cards well. Treated stock scoured five times as above outlined exhibits good carding properties. The presence of montmorillonite on the fiber may also be determined by stain tests. For example, p-phenetidine with acid stains the montmorillonite purple, benzidine dihydrochloride with ammonium hydroxide stains blue, and o-anisidine with alkali stains green.

Example 2 The procedure of Example 1 was repeated except that after circulation of the treating medium through the stock for 5 minutes, two pounds of potassium acetate were added to the circulating liquor, and the treatment then completed. The treated stock was centrifugated and dried without rinsing.

The potassium acetate functions on the treated stock as a humectant material, and assures optimum static control. It has been observed that while the nylon is naturally positive prone, nylon treated in accordance with the present invention is sometimes prone to develop slight negative charge. A humectant material apparently adsorbs moisture from the air onto the surface of the nylon, which moisture conducts away any negative charge which may accumulate, thereby insuring that the treated nylon exhibits a near zero static character.

Example 3 The procedure of Example 1 was repeated, except that phosphoric acid was utilized to bring the pH of the montmorrilonite sol to about 4. In this example, a 0.1% montmorillonite sol was utilized (600 pounds water and .6 pound Volclay 200), and the heated medium was cir- Example 4 Fifty pounds of raw stock: Du Pont Type 200, 3-denier, 1V2" staple fiber, was placed in a standard dye machine of the Morton type, and washed to remove the finish as in Example 1. After draining the water, the machine was filled with 600 pounds of a 3.0% sol of montmorillonite in water (600 pounds water and 18 pounds Volclay 200), and the pH of the sol then adjusted to an initial pH of 3.0 by adding glacial acetic acid.

Du Pont Milling Yellow GN Conc. 250% was then added to the acidified sol, to effect dyeing simultaneously with the montmorillonite treatment. The temperature of the treating medium was then raised to and maintained at 210 F., and the dye machine operated to circulate the medium through the stock for two hours. The medium was then drained and rinsed, centrifuged and dried in an oven at 160. The stock was elfectively treated with the montmorillonite and simultaneously dyed.

' The concentration of the montmorillonite sol utilized in the invention may be as high as 5 or 6% although at such concentrations the dispersion tends to gel, and special efforts must be made to maintain the dispersion in sol form. The preferred range of concentration is fiom about 0.1 to about 3.0% by Weight.

The acidity of the sol may be varied within reasonable limits. In general, the process is carried out best at low pH. A practical lower limit is pH 3.0, lower pH sometimes resulting in degradation of the nylon. The preferred pT range for use in the invention is from about 3.0 to about 6.0. Most common acids may be used to acidify the treating medium. For example, besides acetic and phosphoric, dilute hydrochloric and sulphuric acids may be employed.

The reaction does not proceed well at room temperature, and an elevated temperature of at least about 140 F. is required for satisfactory reaction rate. The reaction rate increases with rise in temperature, evidently due to increased Brownian movement of the montmorillonite particles. The preferred temperature range in the process, accordingly, is from about 140 F. to about 250 F., optimum temperature being about 210 F.

The reaction time may be from about 10 minutes to 2 hours, shorter periods of time being effective with higher temperatures. At temperatures between 160 and 210 F., no measurable increment of reaction occurs after 2 hours. Completion of the reaction is facilitated by agitation and circulation of the medium. Since the nylon progressively removes montmorillonite particles from the medium, it is important to continually bring fresh sol into contact with the nylon surfaces.

Montmorillonite particles fixed to the surfaces of nylon fibers and filaments may serve as a delustering agent. If a humectant material is added, besides potassium acetate, other common humectant material such as calcium chloride, sodium sulphate, glycerin and sorbitol may be employed. In acidifying the treating medium, it is important that the nylon be contacted with the acid only in the presence of the montmorillonite particles. The sol may be acidified before being brought into contact with the nylon, or the acid may be added to the sol while it is in contact with the nylon, as in the examples. It has been found, however, that if the nylon is placed in an acid solution of appropriate pH, and the montmorillonite subsequently added, the reaction will not proceed well.

Conventional acid dyestuffs which can be applied to nylon in a direct manner and are substantive to nylon may be applied simultaneously with the treatment described. As will be evident, in the case of stock which must be dyed in any event, the process of this invention may be performed simultaneously, and accordingly at no additional cost. Besides the dye used in Example 4, examples of similar dyes which may be utilized are Du Pont Milling Orange R Conc., Du Pont Neutral Brown BGL, and Capracyl Blue G. Common expedients customary in applying and fixing dyestuffs of this kind may be performed, without detriment to the process.

It will thus be seen that there has been provided by this invention a process and composition in which the various objects hereinbefore set forth, together with many practical advantages, are successively achieved. As various possible embodiments may be made of the novel features of the above invention, all without departing from the scope thereof, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative, and not in a limiting sense.

I-claim:

1. Process for treatment of nylon comprising contacting nylon with a montmorillonite sol in acid medium, the concentration of montmorillonite in said sol being from about 0.1 to about 3.0% by weight and the pH of said medium being from about 3.0 to about 6.0, at an elevated temperature of from about to about 250 F. for a period of time, from about ten minutes to about two hours, sufiicient to fix montmorillonite particles to the nylon.

2. Process as defined in claim 1, wherein the pH of said medium is approximately 4.

3. Process as defined in claim 1, wherein said medium comprises acetic acid.

4. Process as defined in claim 1, wherein said temperature is approximately 210 F.

5. Process as defined in claim 1, wherein said medium is circulated with respect to said nylon.

6. Process as defined in claim 1, wherein said medium comprises potassium acetate, and said nylon is subsequently removed from said medium and then dried without rinsing.

7. Process as defined in claim 1, wherein said medium comprises a dye substantive to nylon.

8. A composition comprising nylon having montmorillonite particles aflixed thereto, having controlled static properties and resistance to wet and dry soiling, said composition bcing obtained by the process of claim 1.

9. A composition comprising nylon having montmorillonite particles affixed thereto, having controlled static properties and resistance to wet and dry soiling, said particles resisting removal by repeated scourings, said composition being obtained by the process of claim 6.

10. A composition comprising dyed nylon having montmorillonite particles afiixed thereto, having controlled static properties and resistance to wet and dry soiling, said composition being obtained by the process of claim 7.

References Cited in the file of this patent UNITED STATES PATENTS 

1. PROCESS FOR TREATMENT OF NYLON COMPRISING CONTACTING NYLON WITH A MONTOMORILLONITE SOL IN ACID MEDIUM, THE CONCENTRATION OF MONTOMORILLONITE IN SAID SOL BEING FROM ABOUT 0.1 TO ABOUT 3.0% BY WEIGHT AND THE PH OF SAID MEDIUM BEING FROM ABOUT 3.0 TO ABOUT 6.0, AT AN ELEVATED TEMPERATURE OF FROM ABOUT 140* TO ABOUT 250* F. FOR A PERIOD OF TIME, FROM ABVOUT TEN MINUTES TO ABOUT TWO HOURS, SUFFIEIENT TO FIX MONTMORILLONITE PARTICULES TO THE NYLON. 